With evolution of a wireless network, more and more services are provided, which requires additional spectrum resources to support mass data transmission. Operators of cellular radio networks start to discuss how to utilize spectrum resources on the unlicensed bands such as 5 GHz ISM (Industrial Scientific Medical) band on the basis of using the existing LTE network. On the other hand, more and more WiFi systems are being deployed on the unlicensed bands in WiFi wireless industry. The communication systems of different operators have equal rights to use the unlicensed bands. Therefore, it is desired in the industry to solve the problem of how to use the same unlicensed band fairly and effectively. At present, the industry commonly reaches a consensus that the unlicensed bands should be used with the assistance of a licensed band and provide services to terminals in a manner of carrier aggregation.
When performing data transmission on the unlicensed bands, each unlicensed band or each carrier operating on the unlicensed band may have a restriction on a maximum transmission power, which varies according to regulations in different countries or regions. Energy detection shall be performed before transmitting data on the unlicensed band, thus if a fixed power is allocated to each carrier, once the energy detection on a certain carrier is failed, which means that the carrier is unavailable, the power allocated to the carrier will be wasted. Therefore, the inventor considers adding this power to a carrier for which the energy detection is successful, which may significantly improve system performance.
Furthermore, if a base station (such as an eNB) has performed power adjustment but fails to timely notify the user equipment of the adjustment, on one hand, for downlink transmission, CSI (Channel Status Information) measurement and RRM (Radio Resource Management) measurement results (such as RSRP (Reference Signal Reception Power) and/or RSRQ (Reference Signal Reception Quality)) of the user equipment, which are very important for operations such as system resource scheduling, link adaptation (such as modulation coding scheme selection), cell configuration, activation, deactivation and mobility management (cell handover, cell selection), load transfer and the like, may be affected; and on the other hand, for uplink transmission, since a transmission power on the carrier for the uplink transmission of the user equipment is also controlled by the base station, the base station should also notify the user equipment of the power adjustment result for the user equipment to perform uplink data transmission according to the power adjustment result.